This invention relates to a method of producing coated powder material by atomization of a stream of molten metal or metal alloy. The powder preferably comprises wholly or partly coated particles.
In the art of gas atomization of molten metal it is known to introduce ceramic particles into the atomized spray for co-deposition with the atomized metal or metal alloy so as to form a composite deposit. For example, our United Kingdom Patents Nos. 1379261 and 2172827 disclose introducing solid particles into a spray deposit during the deposition operation.
In our International Patent Application published under No. WO89/05870 we also disclosed a method of producing a coherent deposit of an alloy by introducing into a base metal spray particles of a different material which form an alloying addition whereby, on co-deposition, an alloy deposit of the sprayed and introduced material is formed.
It is also known from United Kingdom Patent No. 1298031 to form irregular-shaped powder by injecting metal particles at a spray of molten droplets so that they agglomerate in flight. The injected particles remain solid otherwise the benefits of irregularity would not be achieved. The metal particles are of the same composition and are introduced at a pressure of about 2 barG and are of a fine particle size typically -65 mesh.
From European published Application No. 0262869 it is known to form composite powder where refractory material is introduced into a spray of molten metal so that the refractory material is uniformly distributed within the interior of the particles of the resultant powder.